The present invention relates to optical transducers (sometimes referred to as optical sensors) which utilize optical means for sensing mechanical displacements, such as movements of a body or deformation of a membrane, and converting them to electrical signals. The invention also relates to methods of making such optical transducers. The invention is particularly useful in making optical microphones for converting sound into electrical signals and is therefore described below especially with respect to this application.
Optical transducers of this type are described, for example, in U.S. Pat. Nos. 5,771,091; 5,969,838; 6,091,497; and 6,239,865, and in International Application PCT/IL02/00241 the contents of which patents and application are incorporated herein by reference.
Such optical transducers generally include an optical unit containing a light source, a laterally spaced light detector and a displaceable member aligned with the optical window defined by the light source and light detector. The displaceable members in the optical transducers described in the above patents are generally in the form of deformable membranes, but may be physically movable members, such as in an accelerometer. Optical transducers of this type can be constructed to be very accurate for measuring very small membrane deformations or other displacements.
In general, the known optical transducers do not readily lend themselves to low-cost mass production, and therefore are relatively expense to produce.